The perceptual consequences and neural basis of monocular occlusions

Occluded areas are abundant in natural scenes and play an important role in stereopsis. However, due to the treatment of occlusions as noise by early researchers of stereopsis, this field of study has not seen much development until the last two decades. Consequently, many aspects of depth perception from occlusions are not well understood. The goal of this thesis was to study several such aspects in order to advance the current understanding of monocular occlusions and their neural underpinnings. The psychophysical and computational studies described in this thesis have demonstrated that: 1) occlusions play an important role in defining the shape and depth of occluding surfaces, 2) depth signals from monocular occlusions and disparity interact in complex ways, 3) there is a single mechanism underlying depth perception from monocular occlusions and 4) this mechanism is likely to rely on monocular occlusion geometry. A unified theory of depth computation from monocular occlusions and disparity was proposed based on these findings. A biologically-plausible computational model based on this theory produced results close to observer percepts for a variety of monocular occlusion phenomena

Da Vinci decoded: Does da Vinci stereopsis rely on disparity?

In conventional stereopsis, the depth between two objects is computed based on the retinal disparity in the position of matching points in the two eyes. When an object is occluded by another object in the scene, so that it is visible only in one eye, its retinal disparity cannot be computed. Nakayama and found that a percept of quantitative depth between the two objects could still be established for such stimuli and proposed that this percept is based on the constraints imposed by occlusion geometry. They named this and other occlusion-based depth phenomena ''da Vinci stereopsis.'' Subsequent research found quantitative depth based on occlusion geometry in several other classes of stimuli grouped under the term da Vinci stereopsis. However, Nakayama and Shimojo's findings were later brought into question b

Da Vinci decoded: Does da Vinci stereopsis rely on disparity?

In conventional stereopsis, the depth between two objects is computed based on the retinal disparity in the position of matching points in the two eyes. When an object is occluded by another object in the scene, so that it is visible only in one eye, its retinal disparity cannot be computed. Nakayama and found that a percept of quantitative depth between the two objects could still be established for such stimuli and proposed that this percept is based on the constraints imposed by occlusion geometry. They named this and other occlusion-based depth phenomena ''da Vinci stereopsis.'' Subsequent research found quantitative depth based on occlusion geometry in several other classes of stimuli grouped under the term da Vinci stereopsis. However, Nakayama and Shimojo's findings were later brought into question b

Monocular occlusions determine the perceived shape and depth of occluding surfaces.

Recent experiments have established that monocular areas arising due to occlusion of one object by another contribute to stereoscopic depth perception. It has been suggested that the primary role of monocular occlusions is to define depth discontinuities and object boundaries in depth. Here we use a carefully designed stimulus to demonstrate empirically that monocular occlusions play an important role in localizing depth edges and defining the shape of the occluding surfaces in depth. We show that the depth perceived via occlusion in our stimuli is not due to the presence of binocular disparity at the boundary and discuss the quantitative nature of depth perception in our stimuli. Our data suggest that the visual system can use monocular information to estimate not only the sign of the depth of the occluding surface but also its magnitude. We also provide preliminary evidence that perceived depth of illusory occluders derived from monocular information can be biased by binocular features